In Mario & Luigi: Bowser's Inside Story, Starlow is sent to Princess Peach's meeting as a representative of the Star Sprites. Starlow believes that the cause of the Blorbs was from Blorb Mushrooms sold by a man in a gray cloak. Later, she is inhaled into Bowser, along with Mario, Luigi, and other citizens of the Mushroom Kingdom. When Mario finds her, she is trapped by an amoeba who is holding her inside him. She remarks on how the amoeba is tickling her with rage. She has the same purpose as Stuffwell does in Mario & Luigi: Partners in Time: helping Mario and Luigi. Also like Stuffwell, she holds the Mario Bros. items and equipment. However, the difference between Stuffwell and Starlow is that she has a demo version of all the abilities learned throughout the game. She can combine her powers with Princess Peach to telekinetically control people, such as Bowser, and also help Mario and Luigi to perform certain action commands. Starlow often talks to Bowser from inside of him to give him information. Starlow uses Chippy as her name for Bowser, not wanting him to know that she is helping the Mario Bros. She also helps Mario and Luigi in their encounter with Bowser. She can also save the player from nearly unavoidable attacks from bosses like Bowser, the Dark Star and the Dark Star Core, by having Mario and Luigi grab her feet so she can fly up to the top screen.

Starlow appears to have negative feelings towards Luigi, and this negativity towards him sometimes generates humorous results, such as when Starlow angrily knocks Luigi into Alpha Kretin after Luigi suggests that Starlow fight it alongside Mario rather than him. She only demonstrates this when Luigi is acting particularly cowardly. Also at the cyrogenic chamber at Bowser's Castle, she teases him by saying that he supported his older brother by crying.

At the end of the game, when Bowser hears Starlow's voice, he easily recognizes her as Chippy and gets furious, deciding to pick a fight with the Mario Bros. and her. When Bowser and Peach's Castle were remodelled, Starlow and Birdley deliver a present to Bowser from Peach as a thanks for all he did, and they have a small chat, ending with Starlow teasing him and him yelling at her to leave his castle, which she does.

Starlow returns in Mario & Luigi: Dream Team. She was invited to Pi'illo Island to represent the Star Sprites. Like in the previous game, she acts as Mario and Luigi's partner and guide. She also causes Luigi's in-dream reactions by pulling and tapping on various parts of his face and moving his hand towards buttons. Her looking down on Luigi remains, and Luiginary Works are discovered when she pulls on Luigi's mustache because she is mad at him for causing all the trouble. However, chemistry develops between the two as the game progresses.

Starlow is a cheerful and perky character. This side of her is most apparent talking or getting along with someone she does not know very well, such as Luigi and Bowser. It is also shown that she can get annoyed, such as when Luigi wants her and Mario to fight the Kretin, though she does not hold negative feelings towards Luigi.

Starlow admires Mario's bravery and treats him very kindly, although she doesn't hesitate to speak her mind if she needs to. Her relationship with Luigi starts out far colder in Mario & Luigi: Bowser's Inside Story, with her often expressing annoyance at his cowardice and focusing her attention on Mario. Even so, she acknowledges that he is a hero like his brother, and in Mario & Luigi: Dream Team, she is much more open with him, saying he looks cute when he sleeps and expressing genuine concern when his dreams seem to be troubling him. Starlow claims she's jealous of Luigi's ability to sleep.

Starlow shares a very good friendship with Peach, with the two being very like-minded and even being able to produce powerful combo attacks together. Starlow holds a high amount of respect for the Princess, and puts her safety before anything else. She also gets along well with Prince Dreambert, although his lapses in memory over key pieces of information cause her great frustration, leading her to even call him "Forgetbert" on occasion.

Starlow and Bowser's relationship is dominated by open hostility. She views him as a hotheaded monster and only works with him in Mario & Luigi: Bowser's Inside Story out of necessity, even then knowing to hide her true identity in order to get him to cooperate. Calling herself "Chippy", Starlow directs Bowser from inside of him, but her bossy attitude irritates him as much as his stubbornness vexes her and the two bicker more often than not. Despite that, however, Bowser comes to think of Starlow as a reliable and useful ally and deems her an honorary member of the Koopa Troop, but eventually becomes enraged when he learns the truth about her. Starlow also showed a bit of concern for Bowser, such as when she was worried after Bowser got flattened by his own castle, and felt sorry for him when he was trapped inside his safe. In Mario & Luigi: Dream Team the two are enemies once again, and aside from Bowser's comment that he "hates [Starlow's] voice", no reference is made to their past teamwork. For her part, Starlow views Bowser with disgust and feels that he should give up while he can.

Like Tippi, Kersti and Dreambert, Starlow has the ability to float, and she uses this ability to move around freely in midair. She can also open the Star Menu, which is similar to Stuffwell from the previous games, except it has demos of the special attacks Mario and Luigi have unlocked. In Mario & Luigi: Bowser's Inside Story, Starlow is shown to be quite strong, as inthreeboss battles, she could carry both Mario Bros. easily. In Mario & Luigi: Dream Team, Starlow can summon a gust of wind, but this ability was only seen once in the entire game.

When she teams up with Peach, she can move heavy objects with telekinesis and shoot a pink laser from her star.

Starlow's real name is only mentioned three times in Mario & Luigi: Bowser's Inside Story: at the beginning when she is introduced to the members of the conference, when Mario and Luigi find Peach inside the Flab Zone, and in the ending cutscene after Bowser regurgitates everyone from his body.